Abstract
Ca-Mg-Al hydrotalcites were prepared by coprecipitation from Type S95 steel slag of Shanghai Baosteel Group as supports of ionic liquid in this paper. Five basic ionic liquids [Bmim][CH3COO], [Bmim][HCOO], [Bmim]OH, [Bmim]Br and ChOH were prepared and their catalytic performance on the synthesis of glycerol carbonate by transesterification between dimethyl carbonate and glycerol was investigated. The characterization results indicated that [Bmim]OH is the best ionic liquid (IL) for the transesterification reaction of glycerol carbonate. The hydrotalcites before and after intercalation by ionic liquid were characterized by XRD, FTIR, SEM, EDS and the IL were characterized by FT-IR, 13C-NMR and basicity determination via the Hammett method. The analysis results implied that the dispersion of [Bmim]OH in hydrotalcites reduced the alkali density appropriately and facilitated the generation of glycerol carbonate. The yield of glycerol carbonate and the conversion rate of glycerol reached 95.0% and 96.1%, respectively, when the molar ratio of dimethyl carbonate and glycerol was 3:1, the catalyst dosage was 3 wt%, the reaction temperature was 75 °C and the reaction time was 120 min. The layered structure of hydrotalcites increased the stability of ionic liquid intercalated in carriers, thus the glycerol conversion and the GC yield still remained 91.9% and 90.5% in the fifth reaction cycle.
Highlights
Steel slag is the solid waste composed of Ca, Si, Fe, Mg, Al, Mn, P, O and so on in the steel-making procedure [1]
The layered structure of hydrotalcites increased the stability of ionic liquid intercalated in carriers, the glycerol conversion and the GC
The glycerol conversion and the GC yield mounted up with the increase of basicity while the reaction selectivity decreased because glycerol carbonate was further decarboxylated to generate glycidol in the strong alkaline environment
Summary
Steel slag is the solid waste composed of Ca, Si, Fe, Mg, Al, Mn, P, O and so on in the steel-making procedure [1]. The simple utilization of steel slag usually causes the loss of valuable metal resources due to the massive emissions [2]. The new door to the comprehensive utilization of steel slag will be opened up if the various metal resources can be used for the preparation of new multifunctional materials with high value [3,4]. The host layers and guest anions in LDHs are connected by noncovalent bonds. LDHs have broad application prospects in adsorption, catalysis, biomedicine and other fields due to their unique properties such as pore size tunability, interlayer anion exchangeability [6] and interlayer cation compatibility [7]. LDHs are often used as carriers in the catalysis field due to their layered structures [8]
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